Resilient end washer renewable fuse



Aug. 25, 1953 VON HOORN 2,650,283

' RESILIENT END WASHER RENEWABLE FUSE Filed April 4, 1951 Inventor:

' HOTYW b His Attor ey.

Patented Aug. 25, 1953 RE LIEN ND'WASHER RENEWABLE FUSE Fred .G. yonHoorn, Bridgeport, ..Gnn., .assignor to General Electric Company,acorporation of New York Application April A, 1951 Serial No. 219,205

1Claims. I

My invention relates to renewable electric fuses of the cartridge typeand, particularly, to a resilient .end washerfor such a fuse.

This application is a continuation-in-part of my abandoned applicationSerial lib/176,030, filed July 26, 1950, and assigned to the sameassignee as the present application.

Renewable electric fuses of the cartridge type commonly comprise a pairof spaced terminal strips supported by a bar of insulating material andinterconnected by a fusible strip, or fuse link, as it is generallycalled. This assembly is :then inserted into a cartridge of insulatingmaterial having at least one removable end to form a gas-pressureresisting cylinder with a portion of the terminal strips extending fromeach end. One or both ends of the cartridge are provided with closuresproviding only a restricted escape path for gases generated by blowingof the fuse link.

In this type fuse, dimculty is encountered in securing cartridges andinsulating bars of the proper relative length; that is, due to themanufacturing tolerances the cartridge may be too short for the bar inone instance to produce a buckling or twisting of the bar; or thecartridge may be too long for the bar to produce a loose fit and aninsuficiently restricted seal against internal gas pressures.

It is an object of this invention to provide a cartridge type, renewablefuse structure having a .compensating member to offset manufacturingtolerances while-simultaneously sealing the structure :to force escapinggases produced by a blown link ,to follow a circuitous path effective tocool them before they escape from the fuse cartridge.

Briefly, this invention comprises the combination of a compressible,heat resistant sealing --member with metal end closure member mount- .edon a renewable fuse structure before it is inserted into its cartridgehousing. The compressible sealing member compensates for the differencein length of cooperating fuse link supporting members resulting frommanufacturing tolerances. It simultaneously insures a tight fit betaveencooperating end closure members to direct escaping gases through apredetermined circuitous path, thereby cooling them before they escapefrom the fuse cartridge.

My invention will best be understood from the following description inconnection with the accompanying drawing in which Fig. l is a cutawayview ,of a renewable fuse assembly enclosed in a cartridge with parts ofthe fuse link assembly .cut away; Fig. 2 is a view alon line 22 of Fig.1 looking in the direction of the arrows and Fig. 3 is an end view ofFig. 1.

Referring to Figs. 1, 2 and 3 as amended, a

renewable fuse assembly I is .enclosed within a cartridge 2. Washerstand 4 form the closed end of cartridge 2 having diametral slots of theconfiguration of the narrow portion of a "knife blade terminal 5 whichprojects through the slots. *Wa-sher'3 is secured against shoulders ofblade -5 by washer 54 which is caulked to blade :5. A flat washer 5 isprovided with a diametral slotxhaving the configuration of :the narrowportion of a knife blade terminal projecting through the slot andthejoint'hetweenwasher blade 1 is caulked to be gas-tight. The diameter ofthe washer =6 is somewhat smaller than the inside diameter of that partof the cartridge 2 within which it ispositioned to permit gases escapingfrom the interior of the cartridge to flow around the washer edgestoward the lower end of the fuse assembly. The blade "i' also projectsthrough a loose fitting diametric slot in a flat lower washer 8 andthrough intermediate washers 9 and 6a, the intermediate washers alsohaving diameters smaller than the inside diameter of the cartridge.Washer 9 is made of a resilient material, preferably a compressible,heat resisting, elastomeric material such as silicone rubber or othersuitable material, and washer 8c is suitably made of metal and providedwith a waffle surface bearing against the upper surface of the flatwasher 8 and a flat surface engaging the resilient washer 9. Togetherthe washers B, 8, 9 and to form a resilient end assemblyfor thecartridge 2.

A supporting bar iii of non-conducting material-held in clamps ii and 12extending around bar I 0 and engaging projections on the sides ofterminals 5 and l is secured with a fuse link l3 to terminalsfi andrespectively, by bolts M to form fuse link assembly I. Spacers l5separate bar ID from blades 5 and '1.

To hold the end washer assembly in position, the cartridge 2 is suitablyconstructed with a cylindrical insulating casing l5 having its lower endinternally threaded and engaging one end of an externally threaded metalferrule ll having an inwardly extending flange I 3 against which theedges of the flat washer '8 are biased when the ferrule is threaded intothe casing l6 far enough to compress the resilient washer 9. A similarferrule l 9 is in threaded engagement with the inside of the oppositeend of easing l6 and is provided with a threaded portion protruding fromcasing Hi. The inside surface of fer-rule E9 is provided with axiallyextending notches corresponding to projections 2% on the periphery .ofwasher .4 toprevent ferrule 19 from rotating with respect to blade 5.

A cap 2| is in threaded engagement with ferrule 19- and is provided withan inwardly projecting flange 22 to restrain washer 3 against the end ofthe ferrule l9 to seal that end of the cartridge. As cap 2| is threadedon ferrule l9, blade 5 moves into ferrule l9. Washer 8 moves along blade1 forcing washers 9 and 9a into engagement with washers 6 which isprevented from movement with respect to blade I by engagement with clampl2. Cap 2| is further tightened on ferrule l9 to within a slightclearance distance of casing 16, compressing the resilient washer 9.When the resilient washer 9 is compressed, cartridge 2 is firmly securedto fuse link assembly 1. Thus, the length of casing [6 may be allowed amanufacturing tolerance equal to the maximum depression of washer 9.

As shown in detail in Fig. 3, the waffled lower source of the washer 9a,which surface may also be described as having a plurality ofperpendicular intersectin grooves as in a waflle iron, provides a numberof small cross-sectional area paths from its periphery to the blade 1when in contact with the upper flat surface of washer 8. Consequently,when the washers are tightened into engagement, gases produced by ablown fuse must pass around the outer peripheries of washers 6, 9, and9a, and then along the waffied surface of washer 9a between it andwasher 8 to escape through the clearance slot 23 of washer 8. Thiscombination of elements provides a predetermined cooling path for theescaping gases thereby reducing the temperature of the emitted gases.

Washer 9 in being formed from silicone rubber or other suitableheat-resistant, com-pressible material, provides an element notheretofore recognized in the art. Washer 9 in addition to effecting apredetermined path for the cooling gases provides a low cost means forcompensating for relative length differences in the cartridge 2 andinsulating bar IE), which differences are a natural result of allowablemass production manufacturing tolerances.

With this structure, the fuse assembly I when inserted into cartridge 2has the resilient washer 9 to compensate for relative length differencesof the cooperating members. When cap 2! is tightened into engagementwith ferrule l9, washer 9 is compressed to effect a gas-tight sealbetween the engaging surfaces of washers '6, 9, 9a, and 9. This end isaccomplished and a tight fit is effected between the fuse assembly I andthe cartridge 2 irrespective of the relative lengths of the cooperatingmembers as governed by a1- lowable manufacturing tolerances.

Modifications of this invention will occur to those skilled in the artand it is desired to be understood, therefore, that this invention isnot to be limited to the particular embodiment disclosed, but that theappended claims are meant to cover all the modifications which arewithin the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a renewable fuse having aligned axially spaced apart terminalblades, a link electrically interconnecting said blades, a cylindricalcasing having means including an inturned flange partially closing oneend, and a threaded collar for closing the opposite end, a closure forsaid flange end of said casing for directing escaping gases throughpredetermined fixed paths, said end closure comprising a plurality ofwashers positioned in parallel juxtaposition, each of said washershaving a diameter smaller thanthat of said casing, and each of saidwashers further having a central slot to permit a terminal blade to passtherethrough, the axially outer one of said wash- 4 ers being positionedto engage the periphery of said casing inturned flange, means forming agas tight seal between the axially inner one of said washers and saidterminal blade to force gases about its peripheral edges, and a pair ofwashers lying between said axially inner and outer ones, one of saidpair being of resilient material and the other of said pair having onewafiled face to provide with said axially outer washer circuitousradially inwardly directed passageways to efiect a cooling of gases asthey pass out of said casing.

2. In a renewable fuse having a casing, one fixed end collar, oneremovable end collar, a pair of axially aligned knife blades extendingone through either end collar with one of said blades having an integralshoulder at its axially inner end and an insulating bar interconnectingthe axially inner ends of said knife blades, a venting means forconducting high pressure gases from the fuse casing, said venting meanscomprising at one end of said casing a first pair of centrally slottedaxially spaced washers posi-. tioned on one of the knife blades betweenits integral shoulder and the insulating bar, means forming a gas tightseal between said knife blade and the inner one of said washers, anescape aperture defined between the outer one of said washers and saidknife blade to provide for conducting gases from said fuse casing, and asecond pair of washers axially positioned between said first pair, theouter one of said second pair havin a waffied face contiguous with theouter washer of said first pair to conduct gases radially inwardly tosaid escape aperture, the other Wash-- er of said second pair being madeof elastomeric material to act as a seal between the inner washer ofsaid first pair of washers and said wafiled face washer, saidelastomeric washer being axially compressible to compensate formanufacturing tolerances in said fuse parts.

3. In a renewable fuse structure having a cylindrical casing, a pair ofterminal blades, an insulating bar, clamping means for positioning saidterminal blades in spaced part axially aligned relationship, a fuse linkfor electrically interconnecting said terminal blades, and caps at leastone of which is removable for partially closing the ends of said fusestructure while permitting portions of said terminal blades to extendone from either end, an end closure for providing a predeterminedcoolingpath for the escape of gases under pressure from said casing,said end closure comprising a plurality of washers axially arranged inparallel juxtaposition with all of said washers having both a diametersmaller than that of said casing and a central diametrical slot topermit the passage of a portion of one of said terminal bladestherethrough, the axially outer washer means defining a radial path topermit the escape of gases out of said tube, a resilient washer made ofan elastomeric com-position positioned axially inwardly from said outerwasher means to compensate for length Variances in the fuse parts, andclamping means for effecting a fuse assembly.

FRED G. VON HOORN.

References Cited in the file of this patent UNITED STATES PATENTS Number

